Package groovy.servlet

Class ServletBinding

java.lang.Object
groovy.lang.GroovyObjectSupport
groovy.lang.Binding
groovy.servlet.ServletBinding
All Implemented Interfaces:
GroovyObject
public class ServletBinding extends Binding
Servlet-specific binding extension to lazy load the writer or the output stream from the response.

Eager variables

  • "request" : the HttpServletRequest object
  • "response" : the HttpServletRequest object
  • "context" : the ServletContext object
  • "application" : same as context
  • "session" : shorthand for request.getSession(false) - can be null!
  • "params" : map of all form parameters - can be empty
  • "headers" : map of all request header fields

Lazy variables

  • "out" : response.getWriter()
  • "sout" : response.getOutputStream()
  • "html" : new MarkupBuilder(response.getWriter()) - expandEmptyElements flag is set to true
  • "json" : new JsonBuilder()
As per the Servlet specification, a call to response.getWriter() should not be done if a call to response.getOutputStream() has already occurred or the other way around. You may wonder then how the above lazy variables can possibly be provided - since setting them up would involve calling both of the above methods. The trick is catered for behind the scenes using lazy variables. Lazy bound variables can be requested without side effects; under the covers the writer and stream are wrapped. That means response.getWriter() is never directly called until some output is done using 'out' or 'html'. Once a write method call is done using either of these variable, then an attempt to write using 'sout' will cause an IllegalStateException. Similarly, if a write method call on 'sout' has been done already, then any further write method call on 'out' or 'html' will cause an IllegalStateException.

Reserved internal variable names (see "Methods" below)

  • "forward"
  • "include"
  • "redirect"
If response.getWriter() is called directly (without using out), then a write method call on 'sout' will not cause the IllegalStateException, but it will still be invalid. It is the responsibility of the user of this class to not mix these different usage styles. The same applies to calling response.getOutputStream() and using 'out' or 'html'.

Methods

  • "forward(String path)" : request.getRequestDispatcher(path).forward(request, response)
  • "include(String path)" : request.getRequestDispatcher(path).include(request, response)
  • "redirect(String location)" : response.sendRedirect(location)

  • Constructor Details

    • ServletBinding

      public ServletBinding(jakarta.servlet.http.HttpServletRequest request, jakarta.servlet.http.HttpServletResponse response, jakarta.servlet.ServletContext context)
      Initializes a servlet binding.
      Parameters:
      request - the HttpServletRequest object
      response - the HttpServletRequest object
      context - the ServletContext object

  • Method Details

    • setVariable

      public void setVariable(String name, Object value)
      Binds a servlet variable while protecting the reserved lazy helper names.
      Overrides:
      setVariable in class Binding
      Parameters:
      name - the variable name to bind
      value - the value to expose through the binding

    • getVariables

      public Map getVariables()
      Returns the current binding variables after initializing the lazy servlet helpers.
      Overrides:
      getVariables in class Binding
      Returns:
      the binding variables map

    • getVariable

      public Object getVariable(String name)
      Overrides:
      getVariable in class Binding
      Parameters:
      name - the name of the variable to lookup
      Returns:
      a writer, an output stream, a markup builder or another requested object

    • forward

      public void forward(String path) throws jakarta.servlet.ServletException, IOException
      Forwards the current request to another resource using the same request and response.
      Parameters:
      path - the dispatcher path to forward to
      Throws:
      jakarta.servlet.ServletException - if the target resource fails
      IOException - if request dispatching fails

    • include

      public void include(String path) throws jakarta.servlet.ServletException, IOException
      Includes another resource in the current response.
      Parameters:
      path - the dispatcher path to include
      Throws:
      jakarta.servlet.ServletException - if the target resource fails
      IOException - if request dispatching fails

    • redirect

      public void redirect(String location) throws IOException
      Sends a redirect response to the supplied location.
      Parameters:
      location - the redirect target
      Throws:
      IOException - if the redirect cannot be sent